Most features in mIRC are designed to be network resource-friendly. In this particular case, since the large majority of users don't need the IAL to be filled, making mIRC do this automatically would be a waste of IRC network resources. Many users join channels and idle for extended periods of time, and such an automated feature would end up being the reason for much of their network resource usage. This is why the scripting language supports the IAL, to allow those who need it to use it.
